/*
 * booksave.c - 在文件中保存结构中的内容
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAXTITL 40
#define MAXAUTL 40
#define MAXBKS 10

char * s_gets(char * st, int n);

struct book {
    char title[MAXAUTL];
    char author[MAXAUTL];
    float value;
};

int main(void)
{
    struct book library[MAXBKS];
    int count = 0;

    int index, filecount;

    FILE * pbooks;

    int size = sizeof(struct book);

    if ((pbooks = fopen("book.dat", "a+b")) == NULL) {
        fputs("Can't open book.dat file\n", stderr);
        exit(1);
    }

    rewind(pbooks);
    while (count < MAXBKS && fread(&library[count], size, 1, pbooks) == 1 ) {
        if (count == 0) {
            puts("Current contents of book.dat:");
            printf("%s by %s: $%.2f\n", library[count].title, library[count].author, library[count].value);
        }
        count ++;
    }

    filecount = count;

    if (count == MAXBKS) {
        fputs("The book.bat file is full.", stderr);
        exit(2);
    }

    puts("Please add new book titles.");
    puts("Press [enter] at the start of a line to stopr.");
    while (count < MAXBKS && s_gets(library[count].title ,MAXTITL) != NULL 
            && library[count].title[0] != '\0') {
       puts("Now enter the author.");
       s_gets(library[count].author, MAXAUTL);
       puts("Now enter the value.");
       scanf("%f", &library[count].value);
       while (getchar() != '\n') {
           continue;
       }
       if (count < MAXBKS) {
           puts("Enter the next title.");
       }
       count++;
    }

    if (count > 0) {
        puts("Here is the list of your books:");
        for (index = 0; index < count; index++) {
            printf("%s by %s: $%.2f\n", library[index].title, library[index].author, library[index].value);
        }
        fwrite(&library[filecount],size, count - filecount, pbooks);
    } else {
        puts("No books!? Too bad!\n");
    }
    puts("Bye.\n");
    fclose(pbooks);
    return 0;
}

char * s_gets(char * st, int n)
{
    char * ret_val;
    char * find;
    ret_val = fgets(st, n ,stdin);
    if (ret_val) {
        find = strchr(st, '\n');
        if (find) {
            *find = '\0';
        } else {
            while (getchar() != 'n') {
                continue;
            }
        }
    }
    return ret_val;
}


